1. Field of the Invention
The present invention relates generally to printed circuit boards (PCBs). More particularly, the present invention relates to an apparatus for supporting a PCB substrate while a printing apparatus applies solder paste on a surface of the substrate, and a method of forming the PCB using the apparatus.
2. Description of the Related Art
Various electronic components are mounted on a surface of a printed circuit board (PCB). Conventionally, PCBs are mass-produced by automated equipment through various processes including a screen printing process, a component mounting process, a reflow process, etc.
In the screen printing process of PCB mass production, solder paste in a melted state is applied in a predetermined pattern on a substrate surface so that various electronic components of various shapes may be surface-mounted on the PCB to be in communication with each other. The solder paste is applied using an apparatus called a screen printer. The screen printer presses the solder paste supplied on a mask or a screen having a predetermined pattern with a squeegee and applies the pressed solder paste on the PCB.
When the solder paste is applied on the substrate, a PCB supporting apparatus operates to fix (i.e., hold stationary, clamp or secure) the PCB so that the PCB does not move. The PCB supporting apparatus includes an air cylinder pressing a side surface of the PCB to fix the PCB in order to minimize a movement of the PCB during a printing process.
FIG. 1 is a plan view illustrating a conventional PCB supporting apparatus and FIG. 2 is a side view illustrating the PCB supporting apparatus of FIG. 1.
The conventional PCB supporting apparatus presses side surfaces or edges of a PCB 10 to fix the PCB 10. The conventional PCB supporting apparatus includes a stationary plate 11 supporting one edge of the PCB 10 and a movable plate 12 pressing the other edge of the PCB 10. The movable plate 12 is operated by an air cylinder 13 to press the other edge of the PCB 10. When the PCB 10 is pressed and fixed between the stationary plate 11 and the movable plate 12, a printing operation of applying solder paste on the PCB 10 is then performed.
In the printing operation of applying solder paste on the PCB 10, the solder paste that is supplied on a mask or screen is pressed on the PCB 10 by a squeegee. Therefore, a pressure is applied to the PCB 10 in a printing direction, that is, a direction towards where the squeegee presses the solder paste on the PCB 10.
A squeezing pressure ranges from 3 to 20 kg/cm2. On the other hand, the pressure applied to the movable plate 12 by the air cylinder 13 is at the most approximately 2 kg/cm2. Therefore, when the printing operation of applying solder paste on the PCB 10 is performed and a high squeezing pressure is applied while the air cylinder 13 presses and supports the PCB 10 with low pressure, the PCB 10 may move when, for example, the printing direction is from the stationary plate 11 toward the movable plate 12.
If the PCB 10 moves in the printing direction when printing for minute components (e.g., having dimensions of approximately 0.3-0.6 mm) is performed on the PCB 10, a small movement of the PCB 10 in the printing direction greatly affects the printing operation, and thus degrades the printing quality.
The pressure applied to the PCB 10 by the air cylinder 13 may be increased in order to prevent the PCB 10 from moving, but the PCB 10 may be bent, bowed or damaged due to the applied high pressure.